Head bearing rail joint



Sept. 13, 1 G. R. BURKHARDT ET AL 2,717,739

HEAD BEARING RAIL JOINT Filed May 51, 1951 mf 3 m d T r W. w P MVIM mm Fm r0 MW 5 ur ..M m BB c m m R m 1 m H F F 1? i m I- GE w S O P w.

m o 0 O 5 O moGE zoEEzwuzoQwWwEm ATTO RNEYS of rail shows that thecontact must be confined to the aforesaid sector above the line joiningthe center of the radius of the fillet and the intersection of theunderside of the head with the vertical center line of the section ofthe rail.

In Figure l, the available head bearing area extends from the junctureof the head-web fillet with the web throughout said head-web fillet andincluding a short tangent connecting this fillet with the filletdetermining the under outer portion of the rail head. In Figure 2, theavailable head area is similar to Figure 1, except that the tangent islonger. Thus, if the head of the bar is provided with a short tangent atthe upper and outer terminus of the arc defining the major bearingportion 5, the application of the invention is not altered as indicatedby dotted line 5a in Figure 2.

The wear produced by the conventional head-free bar extends throughoutthe hatched area of Figure 1, but the horizontal hatching on the lefthand side of Figure 1 shows the zone of heaviest wear of the webproduced by the head-free bar B while the vertical hatching shows thelocation of wear that will occur in the preferred area with the presentimproved head bearing bar A.

The point of maximum stress in the rail is substantially at the locationof the point of tangency of the head-web fillets with the web, andprogressively diminishes towards the intersection of the head-web filletwith the head substantially at the point indicated by the radius lineRA. The range of bearing between 4 and 5 is indicated by line 9 andradius line RA. The centroid of the preferred are of bearing support isindicated by line 13 which is above the region of maximum stress.

Figure 1 shows a 1l2-lb. T. R. rail with bar A having its upper innerhead portion shaped so that the position of centroid of the curvedbearing is in the area of low stress under the head. This is the resultof confining the bearing between head and bar above the line 9 joiningthe center of the radius of fillet and the intersection of the verticalcenter line of the rail and the lines 11 defining the underside of thehead of the rail.

The bar B is the usual type of head-free bar in which a substantialportion of the bearing area is below the line 9 drawn from the center ofthe radius of the fillet to the intersection of the vertical center lineand the underside of the head of rail. In this case, the centroid ofbearing is in an area of high stress so that the bearing stresses areadditive to the compressive stresses resulting from the strain of thefillet under eccentric load on the head of the rail.

The force diagrams in Figure 1 indicate that the vertical component ofthe force through the centroid of bearing is much greater with bar Athan with bar B so that more support for the head results with bar Athan bar B and the horizontal component is lower so that less wear is tobe expected in a horizontal direction. The scale in Figure 1 providesready reference to the position of the centroid of the bearing.

Studies have been made of rails and joint bars to determine the effectof controlling the centroid of the curved bearing surfaces under thehead of the rail so the wear of the web would be reduced and so that thecentroid of the bearing would be changed from an area of maximum stressto an area where tests of steel rails and plastic models used withpolarized light have shown the stress to be low.

The maximum stress a max. occurring in the fillets at the junction ofthe head and the web may be expressed as a multiple of the nominalstress at juncture of fillet and web, a nom.=P/ U. Accordingly, a max.:ka nom. where k is the stress concentration factor.

k stress concentration factor 4 Uh =width of web at juncture withfillets Z=length of rail affected Figures 1 and 2 illustrate the forcetriangles above described. In these diagrams the resultant of the forcethrough the centroid of the bearing is indicated as 2. Since this isconstant in magnitude the length of the hypotenuse in each of thetriangles is the same. The resultant is resolved into vertical andhorizontal components to show graphically the relative magnitude of theforce applied to the rail vertically and horizontally. The letter V or Hindicates direction. The subscript A, B, C, or D has reference to thejoint bar with corresponding letter. Referring to Figure 1, it is notedby use of dividers or by marking a piece of paper that VA is about fivedivisions on the scale in Figure l, and HA is three so that withimproved bar A, the vertical force is 1.6 times the horizontal force. VBis three divisions on the scale, and HE is five divisions so that in theold type bar B, the vertical force applied to the rail is only 73 of thehorizontal force applied so wear of the web results instead of wear ofthe metal under the head. Similarly in bar C, V0 is four divisions ofthe scale in Figure 2, and He is three, whereas in the A. R. E. A. typebar D, VD is 3 /2 divisions and HD is slightly more than four.

Our observation of photoelastic exhibits and strain of models indicatesthat there are five principal factors which contribute to the reductionof k, namely:

(1) Distribution of metal in the rail so that the width of the web atthe juncture is substantially equal to the radii of the fillet joininghead and web or within the range of not less than 0.8 times or more than1.6 times the width of the web at the juncture of the web and fillets,as covered in Burkhardt Patent No. 2,577,601.

(2) Control of bearing between rail and joint bar so that the centroidof the curved bearing is in an area of low stress under the head of therail.

(3) The proximity of the centroid to the juncture of web and fillet.

h (:11) The proximity of the centroid to the edge of the (5) The bendingof the flanges of the head as covered by Burkhardt application SerialNo. 568,309 which shows that stress concentration in the fillets is aminimum when the depth of the head is four times the width of the web atthe juncture with the head-web fillets and that the stress concentrationincreases as the depth of the head is reduced.

Figure 2 shows the A.R.E.A. 115 joint bar C with the improved curvedsurface head-free bar, while the head portion of the bar D shown indotted lines is the old standard bar for this rail. The application ofthe invention in this view is the same as that described in connectionwith Figure 1, and is presented to show that the invention is of suchrange and scope as to be applied to all rail sections.

The effect of the proximity to the juncture of web and head-web filletsis seen in Figure 3 which shows that the stress concentration factor kincreases rapidly as the centroid approaches the juncture of web andfillets. The value of k is 76% of the maximum when the centroid of thebearing is in the position occurring in bar B and only 58% with bars Aand C. The stress concentration is 68% with bar D.

We claim:

1. The combination, comprising, a vignoles rail including a head, a web,a base, curved fillets joining the head and web, and joint bars havinghead portions engaging the major portions of the curved fillets, saidhead portions formed on an arc having the same center as the radii ofthe fillets and in initial and permanent bearing engagement therewith inthe zone of lowest stress in the head fillets of the rail, said zonelying between the underside of the head of the rail and the line drawnfrom the center of the head web fillets to the point of intersection ofthe vertical center line of the rail head and the underside of the headof the rail.

2. The combination, comprising, a vignoles rail including a head, a web,a base, curved fillets joining the head and web and joint bars havinghead portions engaging the major portions of the curved fillets, saidhead portion formed on an arc having same center as the radii of thefillets and in initial and permanent engagement above a line drawnthrough the center of the radius describing the headweb fillets and theintersection of the underside of the head and the vertical center of therail section to locate the centroid of the bearing above the region ofmaximum stress.

3. The combination, comprising, a vignoles rail including a head, a web,a base, curved fillets joining the head and web, the radii of saidfillets being not less than 0.8 times and not more than 1.6 times thewidth of said web at the point of juncture of the web and fillets, andjoint bars having head portions engaging the major portions of thecurved fillets, said head portions formed on a an are having the samecenter as the radii of the fillets and in initial and permanent bearingengagement therewith in the zone of lowest stress in the head fillets ofthe rail.

4. The combination, comprising, a vignoles rail in- 1 cluding a head, aweb, a base, fillets joining the head and web, the radii of said filletsbeing not less than 0.8 times and not more than 1.6 times the width ofsaid web at the juncture of the web and the fillets, and joint barshaving the major portion of their hearing area formed on an arc whoseradius is equal to the radii of the fillets joining the head and web,said bearing area engaging and supporting the head-web fillets and railhead above a line drawn from the center of the radius of the filletjoining the head and web of the rail to the intersection of the verticalcenter line of the web with the junction of the intersecting linesdefining the lower limit of the underside of the head of the rail.

5. The combination, comprising, a vignoles rail including a head, a web,a base, fillets joining the head and web, and joint bars having themajor portion of their bearing area formed on an arc whose radius isequal to the radii of the fillets joining the head and web, said bearingarea engaging and supporting the head-web fillets and rail head above aline drawn from the center of the radius of the fillet joining the headand web of the rail to the intersection of the vertical center line ofthe web with the junction of the intersecting lines defining the lowerlimit of the underside of the head of the rail.

6. An improved head bearing rail joint bar for use with vignoles railshaving a head bearing area extending from the juncture of the head-webfillet with the web to juncture with the outer under head fillet and theunderside of the head of the rail, said joint bar having a head whichengages the portion of the head-web fillet in the zone of lowest stressof the fillet lying above a line drawn head-web fillet above a linedrawn from the center of the radius of the said fillet to theintersection of the vertical center line of the rail with the junctionof the intersecting lines defining the lower limit of the underside ofthe head of the rail.

8. The combination, comprising, a vignoles rail including a head, a web,a base, curved fillets joining the head and web, and joint bars havinghead portions engaging the portions of the curved fillets of the railhead lying in the zone of lowest stress of the rail head, said zonecomprising the sector of the fillets lying between the point of tangencyof the fillets with the under side of the head of the rail and the linedrawn between the extremity of the radius of the fillet and theintersection of the plane of the under side of the head of the rail withthe intersection with the vertical center line of the rail, said headportions of the bars being formed on an arc having the same center asthe radii of the rail fillets and in initial and permanent bearingengagement therewith.

9. The combination, comprising, a vignoles rail including a head, a web,a base, curved fillets joining the head and web, and joint bars havinghead portions engaging the portions of the curved fillets of the railhead lying in the zone of lowest stress of the rail head, said zonecomprising the sector of the fillets lying between the point of tangencyof the fillets with the under side of the head of the rail and the linedrawn between the extremity of the radius of the fillet and theintersection of the plane of the under side of the head of the rail withthe intersection with the vertical center line of the rail, the radii ofthe fillets coincident with said line drawn to said intersection beingnot less than 0.8 and not more than 1.6 times the thickness of the Webat the juncture with said head web fillet, said head portions of thebars being formed on an arc having the same center as the radii of therail fillets and in initial and permanent hearing engagement therewith.

References Cited in the file of this patent UNITED STATES PATENTS1,791,390 Thompson Feb. 3, 1931 1,831,227 Clark Nov. 10, 1931 1,967,509Jackson July 24, 1934 OTHER REFERENCES Seely and Ensign: AnalyticMechanics for Engineers, John Wiley and Sons,. 1921, copy of which is inthe Patent Ofiice Scientific Library.

